This application makes reference to and claims all benefits accruing under 35 U.S.C. Section 119 from an application entitled, xe2x80x9cMICRO-BUBBLE ANALYZING APPARATUS FOR HIGH-PURITY GLASS TUBE USING LASER LIGHT SCATTERING,xe2x80x9d filed in the Korean Industrial Property Office on Dec. 6, 2001 and there duly assigned Serial No. 2001-0076818.
1. Field of the Invention
The present invention generally relates to high-purity overcladding glass tubes fabricated by a sol-gel process. More particularly, the present invention relates to an apparatus that is capable of analyzing micro-bubbles of the high-purity overcladding glass tubes three-dimensionally.
2. Description of the Related Art
In general, optical-fiber parent metals are fabricated by vapor deposition and liquid deposition techniques. The most widely used vapor deposition method includes a chemical vapor deposition (CVD) or a modified chemical vapor deposition (MCVD) process, and the sol-gel process is a common liquid deposition. Recently, because of economical efficiency and facility in fabrication, the sol-gel process has been favored over other processes for fabricating large diameter optical-fiber parent metals. The optical-fiber parent metals aforementioned include rod-shaped primary optical-fiber parent metals and tube-type secondary optical-fiber parent metals (over-cladding glass tubes). During the manufacturing stage, it is important to analyze the characteristics of the glass tubes, such as a micro-bubble formed inside the glass tubes.
FIG. 1 is a schematic diagram illustrating a micro-bubble analyzing apparatus for an overcladding glass tube 12 in accordance with one embodiment of a related art. The glass tube 12 shown in FIG. 1 is fabricated by a sol-gel process for use in fabricating the large diameter optical-fiber parent metal using the sol-gel process. Briefly, to fabricate the overcladding glass tube 12, a colloidal sol is first manufactured and injected into a mold to produce a gel to a desired shape. Then, following the consecutive processes of drying, removing organic materials, low-heat treatment and sintering, the glass tube is ultimately fabricated.
However, the high-purity silica glass tube is often degraded due to bubbles and organic byproducts that are sometimes produced during the injection process of the colloidal sol into the mold, whereas micro-bubbles form because the sintering process is not precisely performed. To overcome the problem, a micro-bubble analyzing apparatus depicted in FIG. 1 has been introduced.
As depicted in the drawing, the analyzing apparatus in the related art comprises the glass tube 12 prepared by the sol-gel process at the center, a laser 10 at one side and a screen 14 at the other side. In the FIG. 1, the drawing reference numeral 10a indicates the laser light irradiated to the glass tube, and the 10b indicates a transmitted light after the laser light transmits the glass tube 12. If the laser 10 is vertically irradiated to the outer surface of the glass tube 12, the laser light passes through the glass tube 12 into the interior of the tube and is reflected as an image on the screen placed at the rear surface of the glass tube 12. By analyzing the image on the screen 14, it is possible to evaluate the micro-bubbles remaining inside the glass tube 12.
Still there exists another problem when the laser is vertically irradiated onto the glass tube for the analysis of the transmitted light. That is, it is observed that the light is often distorted as the laser light is reflected, refracted, and dispersed according to the surface state and shape of the cylindrical glass tube. As such, only a rough analysis on the distribution of the micro-bubbles in the glass tube and damages thereon is possible, and a more precise analysis on the micro-bubbles and the damages is not feasible in the current state of art. In addition, the conventional analyzing apparatus is not capable of analyzing the three-dimensional position, size and content level of the micro-bubbles in the glass tube.
The present invention is related to a micro-bubble analyzing apparatus which enables a precise analysis of the conditions of the micro-bubbles of a glass tube.
One aspect of the present invention is to provide a micro-bubble analyzing apparatus that enables the fabrication of high-reliability/high-purity glass tubes.
Accordingly, there is an apparatus for analyzing a micro-bubble inside a glass tube for use in optical-fiber basic materials, which includes: (a) an optical base having a sample stage in a substantially horizontal orientation; (b) a glass tube rotably mounted on the optical base in a substantially vertical orientation, the glass tube being rotated and translated in a vertical direction at a predetermined speed via the sample stage; (c) a light generator disposed at one side of the glass tube for selectively irradiating a laser light onto an outer surface of the glass tube at a prefixed angle; and, (d) a detector disposed at the other side of the glass tube for detecting the distribution and amount of micro-bubbles of the glass tube using the laser light passed through the glass tube.